The nation's top scientists and spies are collaborating on an effort to use the federal government's intelligence assets — including spy satellites and other classified sensors — to assess the hidden complexities of environmental change. They seek insights from natural phenomena like clouds and glaciers, deserts and tropical forests.

The collaboration restarts an effort the Bush administration shut down and has the strong backing of the director of the Central Intelligence Agency. In the last year, as part of the effort, the collaborators have scrutinized images of Arctic sea ice from reconnaissance satellites in an effort to distinguish things like summer melts from climate trends, and they have had images of the ice pack declassified to speed the scientific analysis.

The trove of images is "really useful," said Norbert Untersteiner, a professor at the University of Washington who specializes in polar ice and is a member of the team of spies and scientists behind the effort.